Image recording method

ABSTRACT

Provided is an image recording method including applying an ink containing water, a resin X, and a colorant onto a resin base material A which has a specific distortion rate and to which a tension is applied, to obtain an image, heating the image to a temperature Td and drying the image, and cooling the image to a temperature Tr, in which σ total  calculated by Equation (1) is 40 kgf/cm 2  or less. E(Td) represents an elastic modulus of the resin X at the temperature T d , ε(T d ) represents an expansion coefficient of the resin base material A under specific conditions, E(T) represents an elastic modulus of the resin X at a temperature T of the image in the cooling, α r (T) represents a linear expansion coefficient of the resin X at the temperature T, and α s (T) represents a linear expansion coefficient of the resin base material A under specific conditions. 
       σ total =|σ dry +σ cool |  Equation ( 1 )
 
       σ dry   =E ( T   d )ε( T   d )  Equation ( 2 )
 
       σ cool   =∫E   T     r     T     d   ( T )(α r ( T )−α s ( T )) dT   Equation ( 3 )

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of InternationalApplication No. PCT/JP2020/027294, filed Jul. 13, 2020, the disclosureof which is incorporated herein by reference in its entirety. Further,this application claims priority from Japanese Patent Application No.2019-137001, filed Jul. 25, 2019, the disclosure of which isincorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present disclosure relates to an image recording method.

2. Description of the Related Art

In the related art, a technique of applying an ink to a recording mediumto which a tension is applied to record an image has been known.

For example, WO2017/138436A discloses, as an ink jet recording deviceand an ink jet recording method that enable a recorded material with asatisfactory appearance to be obtained in a state where a high imagequality is maintained even in a case of recording on a resin recordingmedium with an aqueous ink, an ink jet recording device configured suchthat in a case where a recording medium wound on a web roll in a webroll heating and supporting mechanism and recording media directly belowa plurality of ink jet heads are used as a plurality of recording mediummeasurement sites, a plurality of temperature measuring devices measurethe surface temperatures of the plurality of recording mediummeasurement sites, and a heating amount control device controls theheating amount of the web roll heating and supporting mechanism and theheating amount of an underheater such that a difference in temperatureof the recording medium to which the tension has been applied is set to10° C. or lower based on the plurality of measured temperatures, and anink jet recording method using the device.

Further, JP2015-143326A discloses, as an ink that has satisfactoryjetting stability and is capable of achieving the optical density andthe rub resistance of an image at a high level, an ink containing aself-dispersing pigment, acrylic resin particles, a surfactant, awater-soluble organic solvent, and water, in which the surfactantincludes a fluorine-based surfactant having a specific structure andhaving an HLB value of 11 or less which is determined by the Griffinmethod, the water-soluble organic solvent includes at least any of awater-soluble organic solvent selected from the specific group, thetotal content of water-soluble organic solvents of the specific group isfour times or greater the total content of water-soluble organicsolvents out of the specific group, and the sum of the content of theself-dispersing pigment and the content of acrylic resin particles is10% by mass or less with respect to the total mass of the ink.JP2015-143326A discloses an image recording method including a transportstep of transporting a recording medium and an ink applying step ofapplying the ink to the recording medium to which a tension of 20 N/m orgreater is applied.

SUMMARY OF THE INVENTION

However, as a result of examination conducted by the present inventors,it was found that in a case where an image is obtained by applying anink containing water, a resin, and a colorant to a specific resin basematerial in a state where a tension is applied thereto, and the image isrecorded by performing a process of heating, drying, and cooling theobtained image in a state where a tension is applied to the specificresin base material, the adhesiveness between the recorded image and thespecific resin base material is likely to decrease.

An object of one aspect of the present disclosure is to provide a methodof recording an image on a specific resin base material in a state wherea tension is applied thereto, which is an image recording method thatenables suppression of a decrease in adhesiveness between the image tobe recorded and the specific resin base material.

Specific means for achieving the above-described objects include thefollowing aspects.

<1> An image recording method comprising: a step of preparing a resinbase material A in which an absolute value of a distortion raterepresented by Equation (a1) in a case where the base material is heatedfrom 25° C. to 60° C. at a temperature increasing rate of 5° C./min andmaintained at 60° C. for 2 minutes in a state where a tension of 30 N/mis applied thereto, and the base material is cooled to 25° C. at atemperature decreasing rate of 5° C./min in a state where a tension of30 N/m is applied thereto is 0.05% or greater, a step of preparing anink containing water, a resin X, and a colorant, an applying step ofapplying the ink onto the resin base material A to which a tension S1 of10 N/m or greater is applied, to obtain an image, a drying step ofheating and drying the image to a temperature T_(d) of 50° C. or higherin a state where a tension S2 of 10 N/m or greater is applied to theresin base material A, and a cooling step of cooling the image after thedrying step to a temperature T_(r) of 30° C. or lower in a state where atension S3 of 10 N/m or greater is applied to the resin base material A,in which utotal to be calculated by Equation (1) is 40 kgf/cm² or less.

Distortion rate (%)=((length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating)×100  Equation (a1)

σ_(total)=|σ_(dry)+σ_(cool)|  Equation (1)

σ_(dry) =E(T _(d))ε(T _(d))  Equation (2)

σ_(cool) =∫E _(T) _(r) ^(T) ^(d) (T)(α_(r)(T)−α_(s)(T))dT  Equation (3)

In Equation (1), σ_(dry) is calculated by Equation (2), and σ_(cool) iscalculated by Equation (3).

In Equation (2), E(T_(d)) represents an elastic modulus of the resin Xat the temperature T_(d) which is expressed in a unit of kgf/cm²,ε(T_(d)) represents an expansion coefficient of the length of the resinbase material A represented by Equation (a2) in the tension applicationdirection in a case where the base material is heated from 25° C. to thetemperature T_(d) and maintained at the temperature T_(d) in a statewhere the tension S2 is applied thereto, and the base material is cooledto 25° C. in a state where the tension S2 is applied thereto.

Expansion coefficient of length of resin base material A in tensionapplication direction=(length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating  Equation (a2)

In Equation (3), E(T) represents an elastic modulus of the resin X at atemperature T of the image in the cooling step which is expressed in theunit of kgf/cm², α_(r)(T) represents a linear expansion coefficient ofthe resin X at the temperature T, α_(s)(T) represents a linear expansioncoefficient of the resin base material A in the tension applicationdirection in a state where the tension S3 is applied thereto at thetemperature T, T_(d) represents the temperature T_(d), and T_(r)represents the temperature T_(r).

<2> The image recording method according to <1>, in which σ_(total) is30 kgf/cm² or less.

<3> The image recording method according to <1> or <2>, in which thetension S1, the tension S2, and the tension S3 are each independently ina range of 10 N/m to 60 N/m.

<4> The image recording method according to any one of <1> to <3>, inwhich the resin base material A has a thickness of 12 μm to 60 μm.

<5> The image recording method according to any one of <1> to <4>, inwhich the resin base material A is a polypropylene base material or anylon base material.

<6> The image recording method according to any one of <1> to <5>, inwhich the resin X is at least one of an acrylic resin or a polyesterresin.

<7> The image recording method according to any one of <1> to <6>, inwhich the resin base material A has a long film shape, and theapplication of the ink in the applying step, the drying of the image inthe drying step, and the cooling of the image in the cooling step areperformed while the resin base material A is transported in alongitudinal direction of the resin base material A using a roll-to-rollmethod.

According to one aspect of the present disclosure, it is possible toprovide a method of recording an image on a specific resin base materialin a state where a tension is applied thereto, which is an imagerecording method that enables suppression of a decrease in adhesivenessbetween the image to be recorded and the specific resin base material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing the relationship between a temperature T of animage during a cooling step and “E(T) (α_(r)(T)−α_(s)(T))” in an exampleof the image recording method of the present disclosure.

FIG. 2 is a view conceptually illustrating an example of an imagerecording device used for carrying out the image recording method of thepresent disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present disclosure, a numerical range shown using “to” indicatesa range including the numerical values described before and after “to”as a lower limit and an upper limit.

In the present disclosure, in a case where a plurality of substancescorresponding to respective components in a composition are present, theamount of the respective components in the composition indicates thetotal amount of the plurality of substances present in the compositionunless otherwise specified.

In a numerical range described in a stepwise manner in the presentdisclosure, an upper limit or a lower limit described in a certainnumerical range may be replaced with an upper limit or a lower limit inanother numerical range described in a stepwise manner or a valuedescribed in an example.

In the present disclosure, the meaning of the term “step” includes notonly an independent step but also a step whose intended purpose isachieved even in a case where the step is not clearly distinguished fromother steps.

In the present disclosure, a combination of preferred embodiments is amore preferred embodiment.

In the present disclosure, kgf/cm² is a unit in terms of ConversionFormula “1 kgf/cm²=9.80665×10⁻² MPa”.

[Image Recording Method]

An image recording method of the present disclosure includes a step ofpreparing a resin base material A in which an absolute value of adistortion rate represented by Equation (a1) in a case where the basematerial is heated from 25° C. to 60° C. at a temperature increasingrate of 5° C./min and maintained at 60° C. for 2 minutes in a statewhere a tension of 30 N/m is applied thereto, and the base material iscooled to 25° C. at a temperature decreasing rate of 5° C./min in astate where a tension of 30 N/m is applied thereto is 0.05% or greater,a step of preparing an ink containing water, a resin X, and a colorant,an applying step of applying the ink onto the resin base material A towhich a tension S1 of 10 N/m or greater is applied, to obtain an image,a drying step of heating and drying the image to a temperature T_(d) of50° C. or higher in a state where a tension S2 of 10 N/m or greater isapplied to the resin base material A, and a cooling step of cooling theimage after the drying step to a temperature T_(r) of 30° C. or lower ina state where a tension S3 of 10 N/m or greater is applied to the resinbase material A, in which σ_(total) to be calculated by Equation (1) is40 kgf/cm² or less.

Distortion rate (%)=((length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating)×100  Equation (a1)

σ_(total)=|σ_(dry)+σ_(cool)|  Equation (1)

σ_(dry) =E(T _(d))ε(T _(d))  Equation (2)

σ_(cool) =∫E _(T) _(r) ^(T) ^(d) (T)(α_(r)(T)−α_(s)(T))dT  Equation (3)

In Equation (1), σ_(dry) is calculated by Equation (2), and σ_(cool) iscalculated by Equation (3).

In Equation (2), E(T_(d)) represents an elastic modulus of the resin Xat the temperature T_(d) which is expressed in a unit of kgf/cm²,ε(T_(d)) represents an expansion coefficient of the length of the resinbase material A represented by Equation (a2) in the tension applicationdirection in a case where the base material is heated from 25° C. to thetemperature T_(d) and maintained at the temperature T_(d) in a statewhere the tension S2 is applied thereto, and the base material is cooledto 25° C. in a state where the tension S2 is applied thereto.

Expansion coefficient of length of resin base material A in tensionapplication direction=(length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating  Equation (a2)

In Equation (3), E(T) represents an elastic modulus of the resin X at atemperature T of the image in the cooling step which is expressed in theunit of kgf/cm², α_(r)(T) represents a linear expansion coefficient ofthe resin X at the temperature T, α_(s)(T) represents a linear expansioncoefficient of the resin base material A in the tension applicationdirection in a state where the tension S3 is applied thereto at thetemperature T, T_(d) represents the temperature T_(d), and T_(r)represents the temperature T_(r).

The image recording method of the present disclosure is a method ofrecording an image on the resin base material A in a state where atension is applied thereto, which is an image recording method thatenables suppression of a decrease in adhesiveness between the image tobe recorded and the resin base material A.

Hereinafter, the above-described effects will be described in moredetail.

The resin base material A is a resin base material having a largedistortion in a case where the base material is heated and cooled in astate where a tension is applied (specifically, the absolute value ofthe distortion rate (%) is 0.05% or greater).

As a result of examination conducted by the present inventors, it wasfound that in a case where an image is obtained by applying an inkcontaining water, a resin, and a colorant to such a resin base materialA in a state where a tension is applied thereto, and the image isrecorded by performing a process of heating, drying, and cooling theobtained image in a state where a tension is applied to the resin basematerial A, the adhesiveness between the recorded image and the resinbase material A is likely to decrease. Here, the “heating and drying”indicates that the image is heated and dried.

According to the image recording method of the present disclosure, adecrease in the adhesiveness between the image and the resin basematerial A (hereinafter, also simply referred to as “the adhesiveness ofthe image”) in a case where the image is recorded on the resin basematerial A by performing the above-described process can be suppressed.

The reason why the effect of the adhesiveness of the image is exhibitedis assumed as follows.

The decrease in the adhesiveness of the image is considered to occur dueto a large residual stress between the resin base material A and theimage after being heated, dried, and cooled because the absolute valueof the distortion rate of the resin base material A is 0.05% or greater.The residual stress is considered to be due to the residual distortionof the resin base material A.

The stress between the image and the resin base material A is consideredto be mainly generated during the maintaining of the image at thetemperature T_(d) which is the maximum reached temperature in a case ofheating and drying the image and in the process of cooling the image. Itis considered that the final residual stress is determined by adding upthese stresses.

In addition, it is considered that the stress is not generated in theprocess before the temperature of the image reaches the maximum reachedtemperature. The reason for this is considered to be that liquidcomponents such as water remain in the image, and thus the image issoft.

Further, it is considered that the stress due to a difference in thelinear expansion coefficient between the image and the resin basematerial A is not generated in the case of heating and drying the image.The reason for this is that the temperature of the image is maintainedat the temperature T_(d) (that is, at a constant temperature).

In consideration of the above-described points, in the image recordingmethod of the present disclosure, σ_(dry) is acquired as a value thatcorrelates with the stress generated during the maintaining of the imageat the temperature T_(d) (that is, the maximum reached temperature),σ_(cool) is acquired as a value that correlates with the stressgenerated in the process of cooling the image, σ_(total) is acquired asa value that correlates with the final residual stress based on σ_(dry)and σ_(cool), and σ_(total) is limited to 40 kgf/cm² or less. In thismanner, a decrease in adhesiveness between the image and the resin basematerial A is considered to be suppressed because the residual stressbetween the resin base material A and the image is reduced.

Here, σ_(dry) and σ_(cool) each may be a positive value or a negativevalue.

For example, in a case where the resin base material A expands duringthe maintaining of the image at the temperature T_(d) in the case ofheating and drying the image, ε(T_(d)) in Equation (2) is a positivevalue and σ_(dry) is also a positive value.

Further, in a case where the resin base material A contracts during themaintaining of the image at the temperature T_(d) in the case of heatingand drying the image, ε(T_(d)) in Equation (2) is a negative value andσ_(dry) is also a negative value.

Further, in a case where both the resin base material A and the imagecontract in the entire range of the temperature T_(r) to the temperatureT_(d) during the cooling of the image, both the linear expansioncoefficient of (α_(s)(T)) of the resin base material A and the linearexpansion coefficient (α_(r)(T)) of the resin X in the image arepositive values. Here, in a case where α_(s)(T) is smaller than α_(r)(T)in the entire range of the temperature T_(r) to the temperature T_(d)(schematically, in a case where the contraction amount of the resin basematerial A with respect to the temperature decrease is smaller than thecontraction amount of the image with respect to the temperaturedecrease), “α_(r)(T)−α_(s)(T)” in Equation (3) is a positive value, andthus σ_(cool) is also a positive value.

Further, in a case where the resin base material A expands and the imagecontracts in the entire range of the temperature T_(r) to thetemperature T_(d) during the cooling of the image, α_(s)(T) is anegative value and α_(r)(T) is a positive value, and thus“α_(r)(T)−α_(s)(T)” in Equation (3) is a positive value. As a result,σ_(cool) is also a positive value.

Further, in a case where both the resin base material A and the imagecontract in the entire range of the temperature T_(r) to the temperatureT_(d), and α_(s)(T) is larger than α_(r)(T) in the entire range of thetemperature T_(r) to the temperature T_(d) (schematically, in a casewhere the contraction amount of the resin base material A with respectto the temperature decrease is greater than the contraction amount ofthe image with respect to the temperature decrease) during the coolingof the image, “α_(r)(T)−α_(s)(T)” in Equation (3) is a negative value,and thus σ_(cool) is also a negative value.

σ_(total) represents the absolute value of the sum of σ_(dry) andσ_(cool) (Equation (1)) and is a value that correlates with the finalresidual stress.

As an example, even in a case where the stress is generated due to theexpansion of the resin base material A during the maintaining of theimage at the temperature T_(d) in the case of heating and drying theimage (that is, in a case where σ_(dry) is a positive value), σ_(cool)is a negative value in a case where the contraction amount of the resinbase material A with respect to the temperature decrease is larger thanthe contraction amount of the resin X with respect to the temperaturedecrease during the cooling of the image. In this case, σ_(dry) andσ_(cool) cancel each other out, and σ_(total) decreases. This indicatesthat a stress in a direction opposite to the direction of the stressgenerated during the heating and drying of the image is generated due tothe cooling of the image, and as a result, the stress is relaxed and thefinal residual stress decreases.

As another example, in a case where the stress is generated due to theexpansion of the resin base material A during the maintaining of theimage at the temperature T_(d) in the case of heating and drying theimage (that is, in a case where σ_(dry) is a positive value), σ_(cool)is a positive value in a case where the contraction amount of the resinbase material A with respect to the temperature decrease is smaller thanthe contraction amount of the resin X with respect to the temperaturedecrease during the cooling of the image. In this case, σ_(dry) as apositive value and σ_(cool) as a positive value are added up, and thusσ_(total) increases. This indicates that a stress in the same directionas the direction of the stress generated during the heating and dryingof the image is generated due to the cooling of the image, and as aresult, the stress increases and the final residual stress increases.

σ_(dry), σ_(coo)l, and σ_(total) may not necessarily match the actualstress, but even in this case, σ_(total) is still a value thatcorrelates with the final residual stress. ta

Therefore, the actual final residual stress can be decreased bydecreasing σ_(total) to 40 kgf/cm² or less, and as a result, thedecrease in the adhesiveness between the resin base material A and theimage due to the final residual stress can be suppressed.

Hereinafter, first, the resin base material A, σ_(dry), σ_(cool),σ_(total), the tension S1, the tension S2, and the tension S3 in theimage recording method of the present disclosure will be described.

<Resin Base Material A>

In the image recording method of the present disclosure, an image isrecorded on the resin base material A.

The resin base material A is a resin base material A in which anabsolute value of a distortion rate represented by Equation (a1) in acase where the base material is heated from 25° C. to 60° C. at atemperature increasing rate of 5° C./min and maintained at 60° C. for 2minutes in a state where a tension of 30 N/m is applied thereto, and thebase material is cooled to 25° C. at a temperature decreasing rate of 5°C./min in a state where a tension of 30 N/m is applied thereto is 0.05%or greater.

Distortion rate (%)=((length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating)×100  Equation (a1)

In Equation (a1), the “length of resin base material in tensionapplication direction at end of cooling - length thereof in tensionapplication direction at start of heating” indicates a change in lengthof the resin base material A during the maintaining of the resin basematerial A at a temperature of 60° C. in the state where a tension of 30N/m is applied thereto.

In addition, the relationship between the change in the length of theresin base material A in the process of increasing the temperature ofthe resin base material A and the change in the length of the resin basematerial A in the process of decreasing the temperature of the resinbase material A is a relationship that both cancel each other out. Thatis, the total of the expansion amount of the resin base material A inthe process of increasing the temperature of the resin base material A(that is, the expansion amount set to be a positive value in a casewhere the resin base material A expands and set to be a negative valuein a case where the resin base material A contracts, the same applieshereinafter) and the expansion amount of the resin base material A inthe process of decreasing the temperature of the resin base material is0. Therefore, the change in length of the resin base material A duringthe maintaining of the resin base material at a temperature of 60° C. ina state where a tension of 30 N/m is applied thereto is acquired by theexpression of “length of resin base material in tension applicationdirection at end of cooling−length thereof in tension applicationdirection at start of heating”.

The distortion rate (a1) of the resin base material A corresponds to theresidual distortion in a case where the resin base material A in a statewhere a tension is applied is heated and cooled.

The residual distortion corresponds to distortion during the maintainingof the resin base material at a temperature of 60° C. The reason forthis is considered to be that the change in length of the resin basematerial A in the process of increasing the temperature of the resinbase material A and the change in length of the resin base material A inthe process of decreasing the temperature of the resin base material Acancel each other out as described above.

In a case where the resin base material A is used for image recording,since the absolute value of the distortion rate (a1) is 0.05% orgreater, a residual stress caused by the residual distortion is likelyto be generated. Therefore, the resin base material A is a base materialin which the adhesiveness of the image is likely to decrease.

The distortion rate (a1) is a distortion rate measured under theabove-described specific conditions (the tension, the temperatureincreasing rate, the maximum reached temperature, the holding time, thetemperature decreasing rate, the minimum reached temperature, and thelike).

However, the conditions in the image recording method of the presentdisclosure are not limited to the specific conditions described above.

That is, the resin base material A in which the distortion rate (a1) is0.05% or greater is a resin base material in which the adhesiveness ofthe image is likely to decrease because the residual distortion in acase where the resin base material is heated, dried, and cooled underconditions other than the specific conditions is large as compared witha resin base material in which the distortion rate (a1) is less than0.05%.

The image recording method of the present disclosure is a method forimproving the adhesiveness of an image to such a resin base material A.

(Method of Measuring Distortion Rate (a1))

The distortion rate (al) is measured by a tension type measuring methodusing a thermomechanical analyzer. In the examples described below,“TMA4000SE” (manufactured by NETZSCH) is used as the thermomechanicalanalyzer.

The details of the tension type measuring method are as follows.

A tension of 30 N/m is applied to the resin base material by adjustingthe temperature of the resin base material to 25° C., grasping both endsof the resin base material whose temperature has been adjusted with achuck, and applying a force in the tension direction. The tension isappropriately adjusted such that a tension of 30 N/m is maintained untilthe measurement of the distortion rate (a1) is completed.

Next, the resin base material is heated from 25° C. to 60° C. at atemperature increasing rate of 5° C./min.

Next, the resin base material is maintained at a temperature of 60° C.for 2 minutes.

Next, the resin base material is cooled to 25° C. at a temperaturedecreasing rate of 5° C./min.

The distortion rate (a1) is calculated by Equation (a1) based on thelength of the resin base material in the tension application directionat the start of the heating and the length thereof in the tensionapplication direction at the end of the cooling.

The absolute value of the distortion rate (a1) of the resin basematerial A may be 0.05% or greater, and may also be 0.10% or greater,0.15% or greater, or 0.18% or greater.

In general, the adhesiveness of the image is likely to decrease as theabsolute value of the distortion rate (a1) increases, and thus theimprovement range of the adhesiveness in a case where the imagerecording method of the present disclosure is applied increases.

The upper limit of the absolute value of the distortion rate (a1) of theresin base material A is not particularly limited and may be, forexample, 0.80%, 0.53%, 0.26%, or the like.

The shape of the resin base material A is not particularly limited, butit is preferable that the resin base material A has a film shape (thatis, a sheet shape).

The thickness of the resin base material A is not particularly limited,but is preferably in a range of 12 μm to 200 μm, more preferably in arange of 12 μm to 100 μm, still more preferably in a range of 12 μm to60 μm, and even still more preferably in a range of 15 μm to 60 μm.

From the viewpoint of easily applying the tension S1, the tension S2,and the tension S3, it is more preferable that the resin base material Ahas a long film shape (that is, a long sheet shape).

The length of the resin base material A in a case of having a long filmshape is not particularly limited, but is preferably 5 m or greater,more preferably 10 m or greater, and still more preferably 100 m orgreater.

The upper limit of the length of the resin base material A in a case ofhaving a long film shape is not particularly limited and may be, forexample, 10000 m, 8000 m, or 5000 m.

The resin base material A may be subjected to a surface treatment fromthe viewpoint of improving the surface energy.

Examples of the surface treatment include a corona treatment, a plasmatreatment, a flame treatment, a heat treatment, an abrasion treatment,and a light irradiation treatment (UV treatment), but the surfacetreatment is not limited thereto.

The resin base material A is not particularly limited as long as theabsolute value of the distortion rate (a1) is 0.05% or greater, andexamples thereof include a polyethylene base material, a polypropylenebase material, and a nylon base material.

The polyethylene base material may be a stretched polyethylene basematerial or an unstretched polyethylene base material, but a stretchedpolyethylene base material is preferable.

The polypropylene base material may be a stretched polypropylene basematerial or an unstretched polypropylene base material, but a stretchedpolypropylene base material is preferable.

The nylon base material may be a stretched nylon base material or anunstretched nylon base material, but a stretched nylon base material ispreferable.

Examples of the resin base material A include a biaxially stretchedpolypropylene base material “FOR-AQ” (manufactured by Futamura ChemicalCo., Ltd., thickness of 25 μm, distortion rate (al) of 0.18%), asimultaneously biaxially stretched nylon base material “EMBLEM(registered trademark) ON-15” (manufactured by Unitika Ltd., thicknessof 15 μm, distortion rate (a1) of −0.26%), and a monoaxially stretchedpolypropylene base material “PE3K-BT” (manufactured by Futamura ChemicalCo., Ltd., thickness of 23 μm, distortion rate (a1) of 0.23%).

Compared to these examples of the resin base material A, for example,the distortion rate (a1) of a biaxially stretched polyester basematerial “FE2001” (manufactured by Futamura Chemical Co., Ltd.,thickness of 25 μm) is 0.01%.

<σ_(total)>

In the image recording method of the present disclosure, σ_(total) to becalculated by Equation (1) is 40 kgf/cm² or less. σ_(total) may be 0kgf/cm².

σ_(total)=|σ_(dry)+σ_(cool)|  Equation (1)

In Equation (1), σ_(dry) is a value that is calculated by Equation (2)shown below and correlates with the stress between the resin basematerial A and the image during the heat and the drying. σ_(dry) can bea positive value or a negative value.

In Equation (1), σ_(cool) is a value that is calculated by Equation (3)shown below and correlates with the stress between the resin basematerial A and the image during the cooling. σ_(cool) can be a positivevalue or a negative value.

As shown in Equation (1), σ_(total) is an absolute value of the sum ofσ_(dry) and σ_(cool), and is a final (that is, after the heating and thedrying in the drying step and the cooling in the cooling step) valuethat correlates with the residual stress between the resin base materialA and the image.

Further, σ_(total) is calculated by rounding off the first digit afterthe decimal point in the absolute value of the sum of σ_(dry) andσ_(cool).

From the viewpoint of further improving the adhesiveness between theimage and the resin base material A, σ_(total) is preferably 30 kgf/cm²or less, more preferably 20 kgf/cm² or less, and still more preferably10 kgf/cm² or less.

<σ_(dry)>

σ_(dry) is a value to be calculated by Equation (2).

σ_(dry) =E(T _(d))ε(T _(d))  Equation (2)

In Equation (2), E(T_(d)) represents an elastic modulus of the resin Xat the temperature T_(d) which is expressed in a unit of kgf/cm²,ε(T_(d)) represents an expansion coefficient of the length of the resinbase material A represented by Equation (a2) in the tension applicationdirection in a case where the base material is heated from 25° C. to thetemperature T_(d) and maintained at the temperature T_(d) in a statewhere the tension S2 is applied thereto, and the base material is cooledto 25° C. in a state where the tension S2 is applied thereto.

Expansion coefficient of length of resin base material A in tensionapplication direction=(length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating  Equation (a2)

As E(T_(d)) and E(T_(d)), measured values of two significant figures arerespectively applied. The methods of measuring E(T_(d)) and E(T_(d))will be described below.

σ_(dry) is acquired as a value of two significant figures.

σ_(dry) to be calculated by Equation (2) correlates with the stressbetween the resin base material A and the image which is generatedduring the heating and the drying in the drying step (specifically,during the maintaining of the image at the temperature T_(d)).

Hereinafter, this point will be described in more detail.

An image recording method of the present disclosure includes an applyingstep of applying an ink containing water, a resin X, and a colorant ontothe resin base material A to which a tension S1 of 10 N/m or greater isapplied to obtain an image, and a drying step of heating and drying theimage to a temperature T_(d) of 50° C. or higher in a state where atension S2 of 10 N/m or greater is applied to the resin base material A.

The image obtained in the applying step is a layer derived from the ink.

The obtained image is heated and dried in the drying step.

E(T_(d)) in Equation (2) is an elastic modulus (unit: kgf/cm²) of theresin X, which is one component of the ink, at the temperature T_(d).

E(T_(d)) is correlated with the elastic modulus of the image at thetemperature T_(d) (the same applies to E(T) described below).

Further, E(T_(d)) in Equation (2) is an expansion coefficient of theresin base material A represented by Equation (a2) (hereinafter, alsoreferred to as an “expansion coefficient (a2)”) in the tensionapplication direction in a case where the resin base material is heatedfrom 25° C. to the temperature T_(d) and maintained at the temperatureT_(d) in a state where the tension S2 is applied thereto, and is cooledto 25° C. in a state where the tension S2 is applied thereto.

Expansion coefficient of length of resin base material A in tensionapplication direction=(length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating  Equation (a2)

In Equation (a2), the “length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating” indicates a change (that is,distortion) in length of the resin base material A during themaintaining of the image at the temperature of Td in a state where thetension S2 is applied to the resin base material A in the drying step.For the reason, the description of Equation (a1) shown above can bereferred to.

In Equation (2), σ_(dry) is acquired by the product of E(T_(d)) andE(T_(d)) (that is, the expansion coefficient (a2) of the resin basematerial A) described above.

The obtained σ_(dry) is a value that is correlated with the stressgenerated during the maintaining of the image at the temperature T_(d)between the resin base material A and the image.

In addition, Equation (2) is an equation for calculating σ_(dry) relatedto the stress of the image with respect to the resin base material Aunder the following preconditions. The same applies to Equation (3)described below.

The physical properties of the image are correlated with the physicalproperties of the resin X.

The temperature of the resin base material A is equal to the temperatureof the image on the resin base material A.

The length of the image on the resin base material A changes accordingto the change in the length of the resin base material A. Therefore, theproduct of E(T_(d)) (that is, the elastic modulus of the resin X) andE(T_(d)) (that is, the expansion coefficient of the resin base materialA) in Equation (2) substantially corresponds to the product of E(T_(d))(that is, the elastic modulus of the resin X) and the expansioncoefficient of the resin X.

(Method of Measuring E(T_(d)))

E(T_(d)) in Equation (2) is measured as follows.

A release agent layer of a polyethylene terephthalate base materialprovided with a release agent layer is coated with an aqueous dispersionliquid of the resin X, dried, and peeled from the base material, therebypreparing a self-supporting film having a thickness of 50 μm whichcontains the resin X.

Dynamic viscoelasticity measurement is performed on the obtainedself-supporting film using a dynamic viscoelasticity tester under theconditions of a test temperature of 25° C. to 130° C., a temperatureincreasing rate of 5° C./min, and a frequency of 10 Hz, and the elasticmodulus of the film at the temperature T_(d) is acquired based on theobtained results. The obtained elastic modulus thereof at thetemperature T_(d) is defined as E(T_(d)).

In the examples described below, a DVA225 type dynamic viscoelasticitytester (manufactured by ITK Corp.) is used as the dynamicviscoelasticity tester.

(Method of Measuring E(T_(d)))

E(T_(d)) in Equation (2) (that is, the expansion coefficient (a2) of theresin base material A) is measured by a tension type measuring methodusing a thermomechanical analyzer. In the examples described below,“TMA4000SE” (manufactured by NETZSCH) is used as the thermomechanicalanalyzer.

The details of the tension type measuring method are as follows.

The tension S2 is applied to the resin base material by adjusting thetemperature of the resin base material to 25° C., grasping both ends ofthe resin base material A whose temperature has been adjusted with achuck, and applying a force in the tension direction. The tension isappropriately adjusted such that the tension S2 is maintained until themeasurement of the expansion coefficient (a2) is completed.

Next, the resin base material A is heated from 25° C. to the temperatureT_(d) at a temperature increasing rate of 5° C./min.

Next, the resin base material is maintained at the temperature T_(d) for2 minutes.

Next, the resin base material is cooled to 25° C. at a temperaturedecreasing rate of 5° C./min.

The expansion coefficient (a2) is acquired by Equation (a2) based on thelength of the resin base material in the tension application directionat the start of the heating and the length thereof in the tensionapplication direction at the end of the cooling, and the obtained valueis defined as ε(T_(d)).

<σ_(cool)>

σ_(cool) is a value to be calculated by Equation (3).

σ_(cool) =∫E _(T) _(r) ^(T) ^(d) (T)(α_(r)(T)−α_(s)(T))dT  Equation (3)

In Equation (3), E(T) represents an elastic modulus of the resin X at atemperature T of the image in the cooling step which is expressed in theunit of kgf/cm², α_(r)(T) represents a linear expansion coefficient ofthe resin X at the temperature T, α_(s)(T) represents a linear expansioncoefficient of the resin base material A in the tension applicationdirection in a state where the tension S3 is applied thereto at thetemperature T, T_(d) represents the temperature T_(d), and T_(r)represents the temperature T_(r).

Here, the unit of the linear expansion coefficient is 1/K.

A measured value of three significant figures is applied as E(T), andmeasured values of two significant figures are respectively applied asα_(r)(T) and α_(s)(T).

The methods of measuring E(T), α_(r)(T), and α_(s)(T) will be describedbelow.

“α_(r)(T)−α_(s)(T)”, “E(T)(α_(r)(T)−α_(s)(T))”, and ucooi arerespectively acquired as values of two significant figures.

σ_(cool) to be calculated by Equation (3) is correlated with the stressbetween the resin base material A and the image, which is generated inthe process of decreasing the temperature of the image from thetemperature T_(d) to the temperature T_(r) in the cooling step.

Hereinafter, this point will be described in more detail.

The cooling step is a step of cooling the image after the drying step toa temperature T_(r) of 30° C. or lower in a state where a tension S3 of10 N/m or greater is applied to the resin base material A.

Since the temperature of the image and the resin base material Adecreases in the cooling step, a stress is generated due to a differencebetween the linear expansion coefficient of the image and the linearexpansion coefficient of the resin base material A.

In Equation (3), this difference is approximately defined as“α_(r)(T)−α_(s)(T)”.

α_(s)(T) corresponds to the linear expansion coefficient of the resinbase material A in the cooling step. Specifically, α_(s)(T) is thelinear expansion coefficient of the resin base material A in the tensionapplication direction of in a state where the tension S3 is appliedthereto at the temperature T.

α_(r)(T) corresponds to the linear expansion coefficient of the image atthe temperature T. Specifically, α_(r)(T) is the linear expansioncoefficient of the resin X in the tension application direction at thetemperature T. Here, the tension is not considered for α_(r)(T). Thereason for this is that the thickness of the image is sufficiently smallas compared with the thickness of the resin base material A.

The ratio of the thickness of the image to the thickness of the resinbase material A (that is, the thickness ratio [image/resin basematerial]) is preferably 0.5 or less, more preferably 0.3 or less, andstill more preferably 0.2 or less.

The lower limit of the thickness ratio [image/resin base material] isnot particularly limited. The lower limit of the thickness ratio[image/resin base material] may be, for example, 0.005, 0.01, or 0.05.

Equation (3) includes “E(T)(α_(r)(T)−α_(s)(T))” which is the product of“α_(r)(T)−α_(s)(T)” and the elastic modulus (E(T)) of the resin X at thetemperature T (that is, the temperature of the image in the coolingstep). The “E(T)(α_(r)(T)−α_(s)(T))” is correlated with the stress atthe time point at which the temperature of the image and the resin basematerial A reaches the temperature T. In Equation (3), the integratedvalue of the “E(T)(α_(r)(T)−α_(s)(T))” from the temperature T_(d) to thetemperature T_(r) is defined as σ_(cool).

The obtained σ_(cool) is correlated with the stress between the resinbase material A and the image, which is generated in the process ofdecreasing the temperature of the image from the temperature T_(d) tothe temperature T_(r) in the cooling step.

σ_(cool) to be calculated by Equation (3) is acquired as follows.

E(T), α_(r)(T), and α_(s)(T) are measured for each temperature Tobtained by dividing a range of the temperature T_(r) or higher and thetemperature T_(d) or lower at intervals of 0.1° C.

“E(T)(α_(r)(T)−α_(s)(T))” at each of the above-described temperatures Tis acquired based on the obtained results.

A graph showing the relationship between the temperature T and“E(T)(α_(r)(T)−α_(s)(T))” is prepared, an area enclosed by the curve ofthe obtained graph, the straight line showing the temperature T_(r), thestraight line showing the temperature T_(d), and the straight line inwhich “E(T)(α_(r)(T)−α_(s)(T))” is 0 is acquired, and the integratedvalue of “E(T)(α_(r)(T)−α_(s)(T))” from the temperature T_(d) to thetemperature T_(r), that is, σ_(cool) is acquired based on the obtainedarea. As described above, σ_(cool) can be a positive value or a negativevalue.

FIG. 1 is a graph showing the relationship between the temperature T ofthe image during the cooling step and “E(T) (α_(r)(T)−α_(s)(T))” in anexample of the image recording method of the present disclosure.

In the example, σ_(cool) is acquired based on the area of the shadedportion in FIG. 1.

(Method of Measuring E(T))

E(T) at each temperature T is measured in the same manner as E(T_(d))except that the measurement temperature is changed to each temperatureT.

(Method of Measuring α_(r)(T))

α_(r)(T) at each temperature T is measured as follows.

A self-supporting film containing the resin X is prepared in the samemanner as that for the self-supporting film prepared in the measurementof E(T_(d)).

A 5 mm×5 mm square sample is cut out from the obtained self-supportingfilm, and the linear expansion coefficient of the cut-out sample at eachtemperature T is measured by a compression type measuring method using athermomechanical analyzer. In the examples described below, “TMA4000SE”(manufactured by NETZSCH) is used as the thermomechanical analyzer.

The details of the compression type measuring method are as follows.

The temperature of the sample is adjusted to 25° C., and a weight of 1kPa is applied to the sample whose temperature has been adjusted to 25°C. in the thickness direction of the sample. In this state, the linearexpansion coefficient of the sample at each temperature T is measuredwhile the temperature of the sample is changed. The obtained linearexpansion coefficient is defined as α_(r)(T) at each temperature T (thatis, the linear expansion coefficient of the resin X at the temperatureT).

(Method of Measuring α_(s)(T))

α_(s)(T) at each temperature T is measured by a tension type measuringmethod using a thermomechanical analyzer. In the examples describedbelow, “TMA4000SE” (manufactured by NETZSCH) is used as thethermomechanical analyzer.

The details of the tension type measuring method are as follows.

The tension S3 is applied to the resin base material A by adjusting thetemperature of the resin base material A to 25° C., grasping both endsof the resin base material A whose temperature has been adjusted to 25°with a chuck, and applying a force in the tension direction. The tensionis appropriately adjusted such that the tension S3 is maintained untilthe measurement of the linear expansion coefficient is completed.

In the above-described state, the linear expansion coefficient of theresin base material A at each temperature T is measured while thetemperature of the resin base material A is changed. The obtained valueis defined as α_(s)(T) at each temperature T.

<Tension S1, Tension S2, and Tension S3>

In the image recording method of the present disclosure, the tension S1,the tension S2, and the tension S3 are each independently a tension of10 N/m or greater. That is, an aspect in which all the tension S1, thetension S2, and the tension S3 are the same as each other, an aspect inwhich only two of the tension S1, the tension S2, and the tension S3 arethe same as each other and the rest is different from the two, or anaspect in which all the tension S1, the tension S2, and the tension S3are different from each other may be employed.

The tension S1, the tension S2, and the tension S3 are eachindependently preferably in a range of 10 N/m to 60 N/m, more preferablyin a range of 10 N/m to 50 N/m, still more preferably 10 N/m to 40 N/m,and even still more preferably in a range of 10 N/m to 30 N/m.

From the viewpoint of the efficiency of image recording, the variationof the tension S1, the tension S2, and the tension S3 represented by thefollowing equation is preferably in a range of 0% to 40%, morepreferably in a range of 0% to 20%, and still more preferably 0% to 10%.

Variation (%) of tension S1, tension S2, and tension S3=(((Maximum valueof tension S1, tension S2, and tension S3)−(minimum value of tension S1,tension S2, and tension S3))/((maximum value of tension S1, tension S2,and tension S3)+(minimum value of tension S1, tension S2, and tensionS3)))×100

The tension S1, the tension S2, and the tension S3 are respectivelymeasured by a tension meter.

The tension S1, the tension S2, and the tension S3 may be respectivelyadjusted using a control device (for example, a tension controller).

The method of applying the tension S1, the tension S2, and the tensionS3 to the resin base material A is not particularly limited, and a knownmethod can be appropriately used.

For example, according to the image recording method in an aspect inwhich the application of the ink in the applying step, the drying of theimage in the drying step, and the cooling of the image in the coolingstep are performed while the resin base material A having a long filmshape is transported in a longitudinal direction using a roll-to-rollmethod, the operation of the applying step is easily performed while thetension S1 is applied to the resin base material A, the operation of thedrying step is easily performed while the tension S2 is applied thereto,and the operation of the cooling step is easily performed while thetension S3 is applied thereto. Here, the tension to be applied to theresin base material A may be adjusted to be constant over the entiretransport path.

Here, the roll-to-roll method indicates a transport method in which along film wound in a roll shape is continuously transported while beingunwound and the continuously transported long film is wound in a rollshape again.

Further, examples of the aspect of the image recording device of thepresent disclosure include, in addition to the above-described aspects,an aspect in which each operation of the applying step, the drying step,and the cooling step is performed on the resin base material A having ashort film shape using a jig or the like while the tension is applied.

Further, in the image recording method of the present disclosure, thetension applied to the resin base material A is maintained at preferably10 N/m or greater (more preferably in a range of 10 N/m to 60 N/m, stillmore preferably in a range of 10 N/m to 50 N/m, even still morepreferably in a range of 10 N/m to 40 N/m, and even still morepreferably in a range of 10 N/m to 30 N/m) in the entire process fromthe start of the applying step to the end of the cooling step.

Hereinafter, each step of the image recording method of the presentdisclosure will be described.

<Step of Preparing Resin Base Material A>

The image recording method of the present disclosure includes a step ofpreparing the resin base material A.

The step of preparing the resin base material A may be a step of simplypreparing the resin base material A produced in advance in order tocarry out the steps after the applying step described below or a step ofproducing the resin base material A.

Further, the step may be a step of performing a surface treatment on theresin base material to obtain the resin base material A.

The resin base material A and the preferred aspects are as describedabove.

<Step of Preparing Ink>

The image recording method of the present disclosure includes a step ofpreparing an ink.

The step of preparing an ink may be a step of simply preparing the inkproduced in advance in order to carry out the steps after the applyingstep described below or a step of producing the ink.

The ink contains water, the resin X, and the colorant.

(Water)

The ink contains water.

The content of water is preferably 50% by mass or greater and morepreferably 60% by mass or greater with respect to the total amount ofthe ink.

The upper limit of the content of water depends on the amount of othercomponents, but is preferably 90% by mass or less and more preferably80% by mass or less with respect to the total amount of the ink.

(Resin X)

The ink contains the resin X.

The resin X is a resin that satisfies Equation (1) to Equation (3) shownabove.

The resin X may be used alone or in the form of a mixture of two or morekinds of resins.

The ink may contain a resin other than the resin X or may not contain aresin other than the resin X.

The proportion of the resin X (the total amount of the two or more kindsof the resins X in a case where two or more kinds of the resins X arepresent) in all the resin components contained in the ink is preferablyin a range of 50% by mass to 100% by mass, more preferably in a range of60% by mass to 100% by mass, and still more preferably in a range of 80%by mass to 100% by mass.

Examples of the resin X include a polyester resin, a polyurethane resin,an acrylic resin, a polyamide resin, a polyurea resin, a polycarbonateresin, a polyolefin resin, and a polystyrene resin.

From the viewpoint of easily satisfying Equation (1) to Equation (3), atleast one of an acrylic resin, a polyester resin, or a polyurethaneresin is preferable, and at least one of an acrylic resin or a polyesterresin is more preferable as the resin X.

In the present disclosure, the acrylic resin indicates a polymer (ahomopolymer or a copolymer) of a raw material monomer containing atleast one selected from the group consisting of acrylic acid, aderivative of acrylic acid (such as acrylic acid ester), methacrylicacid, and a derivative of methacrylic acid (such as methacrylic acidester).

The weight-average molecular weight (Mw) of the resin X is preferably ina range of 1000 to 300000, more preferably in a range of 2000 to 200000,and still more preferably in a range of 5000 to 100000.

In the present disclosure, the weight-average molecular weight (Mw)indicates a value measured by gel permeation chromatography (GPC) unlessotherwise specified.

The measurement according to gel permeation chromatography (GPC) isperformed using HLC (registered trademark)-8020GPC (manufactured byTosoh Corporation) as a measuring device, three columns of TSKgel(registered trademark) Super Multipore HZ-H (manufactured by TosohCorporation, 4.6 mmID×15 cm), and tetrahydrofuran (THF) as an eluent.Further, the measurement is performed under measurement conditions of asample concentration of 0.45% by mass, a flow rate of 0.35 ml/min, asample injection volume of 10 μl, and a measurement temperature of 40°C. using an RI detector.

Further, the calibration curve is prepared using eight samples of“F-40”, “F-20”, “F-4”, “F-1”, “A-5000”, “A-2500”, “A-1000”, and“n-propylbenzene” which are “Standard Samples TSK standard, polystyrene”(manufactured by Tosoh Corporation).

A form of resin particles is preferable as the form of the resin X inthe ink.

That is, it is preferable that the ink contains resin particles as theresin X.

It is preferable that the resin X in this case is a water-insolubleresin.

In the present disclosure, the term “water-insoluble” indicates aproperty in which the amount of a substance to be dissolved in 100 g ofwater at 25° C. is less than 1.0 g (more preferably less than 0.5 g).

The volume average particle diameter of the resin particles serving asthe resin X is preferably in a range of 1 nm to 300 nm, more preferablyin a range of 3 nm to 200 nm, and still more preferably in a range of 5nm to 150 nm.

In the present disclosure, the volume average particle diameterindicates a value measured using a laser diffraction scattering typeparticle size distribution analyzer.

As a measuring device, a particle size distribution measuring device“MICROTRAC MT-33001I” (manufactured by Nikkiso Co., Ltd.) isexemplified.

As the resin particles serving as the resin X, acrylic resin particles,ester resin particles, a mixture of acrylic resin particles and esterresin particles, composite particles containing an acrylic resin and anester resin, or polyurethane resin particles are preferable, and acrylicresin particles, ester resin particles, a mixture of acrylic resinparticles and ester resin particles, or composite particles containingan acrylic resin and an ester resin are more preferable.

The resin X in the resin particles (C) has preferably an alicyclicstructure or an aromatic ring structure and more preferably an aromaticring structure.

As the alicyclic structure, an alicyclic hydrocarbon structure having 5to 10 carbon atoms is preferable, and a cyclohexane ring structure, adicyclopentanyl ring structure, a dicyclopentenyl ring structure, or anadamantane ring structure is preferable.

As the aromatic ring structure, a naphthalene ring or a benzene ring ispreferable, and a benzene ring is more preferable.

The amount of the alicyclic structure or the aromatic ring structure is,for example, preferably in a range of 0.01 mol to 1.5 mol and morepreferably in a range of 0.1 mol to 1 mol per 100 g of the resinparticles X.

It is preferable that the resin X in the resin particles contains anionic group in the structure.

The ionic group may be an anionic group or a cationic group, but ananionic group is preferable from the viewpoint of ease of introduction.

The anionic group is not particularly limited, but a carboxy group or asulfo group is preferable, and a sulfo group is more preferable.

The amount of the ionic group is not particularly limited, and the ionicgroup can be preferably used in a case where the amount thereof is setsuch that the resin particles X are water-dispersible resin particles.For example, the amount thereof is preferably in a range of 0.001 mol to1.0 mol and more preferably in a range of 0.01 mol to 0.5 mol, per 100 gof the resin contained in the resin particles X.

The content of the resin X in the ink is not particularly limited.

The content of the resin X is preferably in a range of 0.5% by mass to30% by mass, more preferably in a range of 1% by mass to 20% by mass,and particularly preferably in a range of 1% by mass to 15% by mass withrespect to the total amount of the ink.

(Colorant)

The ink contains at least one colorant.

The colorant is not particularly limited and known colorants can beused. Among known colorants, an organic pigment or an inorganic pigmentis preferable.

Examples of the organic pigment include an azo pigment, a polycyclicpigment, a chelate dye, a nitro pigment, a nitroso pigment, and anilineblack. Among these, an azo pigment and a polycyclic pigment are morepreferable.

Examples of the inorganic pigment include titanium oxide, iron oxide,calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow,cadmium red, chrome yellow, and carbon black. Among these, carbon blackis particularly preferable.

Preferred examples of the colorant include the colorants described inparagraphs 0096 to 0100 of JP2009-241586A.

The content of the colorant is preferably in a range of 1% by mass to25% by mass, more preferably in a range of 2% by mass to 20% by mass,and particularly preferably in a range of 2% by mass to 15% by mass withrespect to the total amount of the ink.

(Dispersant)

The ink may contain a dispersant used for dispersing the colorant. Asthe dispersant, any of a polymer dispersant or a low-molecular-weightsurfactant-type dispersant may be used. Further, as the polymerdispersant, any of a water-soluble dispersant or a water-insolubledispersant may be used.

Preferred examples of the dispersant include dispersants described inparagraphs 0080 to 0096 of JP2016-145312A.

The mixing mass ratio between a colorant (p) and a dispersant (s) (p:s)is preferably in a range of 1:0.06 to 1:3, more preferably in a range of1:0.125 to 1:2, and still more preferably in a range of 1:0.125 to1:1.5.

(Water-Soluble Organic Solvent Having Boiling Point of 210° C. or Lower)

It is preferable that the ink contains at least one water-solubleorganic solvent having a boiling point of 210° C. or lower.

In this manner, the jettability of the ink can be further improved.

In the present disclosure, the term “water-soluble” indicates a propertythat 1 g or greater (preferably 5 g or greater and more preferably 10 gor greater) of a substance is dissolved in 100 g of water at 25° C.

In the present disclosure, the “boiling point” is a boiling point at 1atm (101325 Pa).

Examples of the water-soluble organic solvent having a boiling point of210° C. or lower include propylene glycol (boiling point of 188° C.),propylene glycol monomethyl ether (boiling point of 121° C.), ethyleneglycol (boiling point of 197° C.), ethylene glycol monomethyl ether(boiling point of 124° C.), propylene glycol monoethyl ether (boilingpoint of 133° C.), ethylene glycol monoethyl ether (boiling point of135° C.), propylene glycol monopropyl ether (boiling point of 149° C.),ethylene glycol monopropyl ether (boiling point of 151° C.), propyleneglycol monobutyl ether (boiling point of 170° C.), ethylene glycolmonobutyl ether (boiling point of 171° C.), 2-ethyl-1-hexanol (boilingpoint of 187° C.), dipropylene glycol monomethyl ether (boiling point of188° C.), diethylene glycol dimethyl ether (boiling point of 162° C.),diethylene glycol diethyl ether (boiling point of 188° C.), anddipropylene glycol dimethyl ether (boiling point of 175° C.).

In a case where the ink contains a water-soluble organic solvent havinga boiling point of 210° C. or lower, the content of the water-solubleorganic solvent having a boiling point of 210° C. or lower is preferablyin a range of 1% by mass to 30% by mass, more preferably in a range of5% by mass to 30% by mass, still more preferably in a range of 10% bymass to 30% by mass, and even still more preferably in a range of 15% bymass to 25% by mass with respect to the total amount of the ink.

(Organic Solvent Having Boiling Point of Higher than 210° C.)

The content of the organic solvent having a boiling point of higher than210° C. in the ink is preferably less than 1% by mass. In this manner,the drying properties of the ink are enhanced.

Here, the expression “the content of the organic solvent having aboiling point of higher than 210° C. in the ink is less than 1% by mass”indicates that the ink does not contain the organic solvent having aboiling point of higher than 210° C. or even in a case where the inkcontains the organic solvent, the content of the organic solvent havinga boiling point of higher than 210° C. is less than 1% by mass withrespect to the total amount of the ink.

The expression “the content of the organic solvent having a boilingpoint of higher than 210° C. in the ink is less than 1% by mass” roughlyindicates that the ink does not substantially contain the organicsolvent having a boiling point of higher than 210° C.

Examples of the organic solvent having a boiling point of higher than210° C. include glycerin (boiling point of 290° C.), 1,2-hexanediol(boiling point of 223° C.), 1,3-propanediol (boiling point of 213° C.),diethylene glycol (boiling point of 245° C.), diethylene glycolmonobutyl ether (boiling point of 230° C.), triethylene glycol (boilingpoint of 285° C.), dipropylene glycol (boiling point of 232° C.),tripropylene glycol (boiling point 267° C.), trimethylolpropane (boilingpoint of 295° C.), 2-pyrrolidone (boiling point of 245° C.),tripropylene glycol monomethyl ether (boiling point of 243° C.), andtriethylene glycol monomethyl ether (boiling point of 248° C.).

(Other Additives)

The ink may contain components other than the components describedabove.

Examples of other components include known additives such as adiscoloration inhibitor, an emulsification stabilizer, a penetrationenhancer, an ultraviolet absorbing agent, a preservative, anantibacterial agent, a pH adjuster, a surface tension adjuster, anantifoaming agent, a viscosity adjuster, a dispersion stabilizer, a rustinhibitor, and a chelating agent.

(Preferable Physical Properties of Ink)

The viscosity of the ink is preferably 1.2 mPa·s or greater and 15.0mPa·s or less, more preferably 2 mPa·s or greater and less than 13mPa·s, and still more preferably 2.5 mPa·s or greater and less than 10mPa·s.

The viscosity in the present disclosure is a value measured at 25° C.using a viscometer. As the viscometer, for example, a VISCOMETER TV-22type viscometer (manufactured by Toki Sangyo Co., Ltd.) can be used.

The surface tension of the ink is preferably 25 mN/m or greater and 40mN/m or less and more preferably 27 mN/m or greater and 37 mN/m or less.

The surface tension in the present disclosure is a value measured at atemperature of 25° C.

The surface tension can be measured using, for example, an AutomaticSurface Tensiometer CBVP-Z (manufactured by Kyowa Interface Science Co.,Ltd.).

From the viewpoint of the dispersion stability, the pH of the ink of thepresent disclosure at 25° C. is preferably in a range of 6 to 11, morepreferably in a range of 7 to 10, and still more preferably in a rangeof 7 to 9.

The pH in the present disclosure indicates a value measured using a pHmeter.

<Applying Step>

The applying step in the image recording method of the presentdisclosure is a step of applying the ink onto the resin base material Ato which tension S1 is applied, to obtain an image.

Only one or two or more kinds of inks may be applied.

For example, in a case where inks of two or more colors are applied,images with two or more colors can be recorded.

As the method of applying the ink, a known method such as a coatingmethod, an ink jet method, or a dipping method can be used.

Among these, an ink jet method is preferable.

The method of jetting the ink in the ink jet method is not particularlylimited, and any of known methods such as an electric charge controlmethod of jetting an ink using an electrostatic attraction force, adrop-on-demand method (pressure pulse method) using a vibration pressureof a piezoelectric element, an acoustic ink jet method of jetting an inkusing a radiation pressure by converting an electric signal into anacoustic beam and irradiating the ink with the acoustic beam, and athermal ink jet (bubble jet (registered trademark)) method of heating anink to form air bubbles and using the generated pressure may be used.

As the ink jet method, particularly, an ink jet method, described inJP1979-59936A (JP-554-59936A), of jetting an ink from a nozzle using anaction force caused by a rapid change in volume of the ink after beingsubjected to an action of thermal energy can be effectively used.

Further, as the ink jet method, the method described in paragraphs 0093to 0105 of JP2003-306623A can also be employed.

The ink is applied by jetting the ink from a nozzle of an ink jet head.

Examples of the system of the ink jet head include a shuttle system ofperforming recording while scanning a short serial head in the widthdirection of the resin base material A and a line system of using a linehead in which recording elements are aligned in correspondence with theentire area of one side of the resin base material A.

In the line system, image recording can be performed on the entiresurface of the resin base material A by scanning the resin base materialA in a direction intersecting the direction in which the recordingelements are aligned. In the line system, a transport system such as acarriage that scans a short head in the shuttle system is not necessary.Further, in the line system, since movement of a carriage andcomplicated scanning control between the head and the resin basematerial A are not necessary as compared with the shuttle system, onlythe resin base material A moves. Therefore, according to the linesystem, image recording at a higher speed than that of the shuttlesystem can be realized.

From the viewpoint of obtaining a high-definition image, the liquiddroplet amount of the ink to be jetted from the nozzle of the ink jethead is preferably in a range of 1 pico liter (pL) to 10 pL and morepreferably in a range of 1.5 pL to 6 pL.

Further, from the viewpoints of improving the image unevenness andimproving connection of continuous gradations, it is also effective thatthe ink is jetted by combining different liquid droplet amounts.

The amount of the ink to be applied in the applying step may be adjustedin consideration of the thickness of the image after the drying step.

The thickness of the image after the drying step is preferably in arange of 0.1 μm to 10 μm, more preferably in a range of 0.3 μm to 7 μm,still more preferably in a range of 0.7 μm to 7 μm, and even still morepreferably in a range of 1 μm to 4 μm.

<Drying Step>

The drying step in the image recording method of the present disclosureis a step of heating the image to a temperature T_(d) of 50° C. orhigher and drying the image in a state where the tension S2 is appliedto the resin base material A.

Examples of the means for heating the image include known heating meanssuch as a heater, known air blowing means such as a dryer, and means forcombining these.

Examples of the method for heating the image include a method ofapplying heat using a heater or the like from a side of the resin basematerial A opposite to an image-forming surface, a method of applyingwarm air or hot air to an image-forming surface of the resin basematerial A, a method of applying heat using an infrared heater from aside of an image-forming surface of the resin base material A and/orfrom a side of an image-non-forming surface of the resin base materialA, and a method of combining a plurality of these methods.

From the viewpoint of image drying efficiency, the temperature T_(d) ispreferably 55° C. or higher and more preferably 60° C. or higher.

From the viewpoint of easily satisfying Equation (1) to Equation (3),the temperature T_(d) is preferably 80° C. or lower, more preferably 70°C. or lower, still more preferably lower than 70° C., and even stillmore preferably 65° C. or lower.

Here, the temperature T_(d) indicates the temperature of the surface ofthe image, which is a value measured using a contactless thermometer(the same applies to the temperature T and the temperature T_(r)described later).

From the viewpoint of the adhesiveness between the image and the resinbase material A, the drying time of the image is preferably 5 seconds orlonger.

From the viewpoint of productivity of image recording, the drying timeof the image is preferably shorter than 30 seconds, more preferablyshorter than 20 seconds, still more preferably 15 seconds or shorter,and even still more preferably 10 seconds or shorter.

Here, the drying time of the image is a time period from the start ofheating the image to the start of cooling of the image.

According to the image recording method of the present disclosure, sincethe utotai is 40 kgf/cm² or less, the adhesiveness between the image andthe resin base material A can be ensured even in a case where the dryingtime is shortened (for example, in a case where the drying time is setto 10 seconds or shorter).

<Cooling Step>

The cooling step in the image recording method of the present disclosureis a step of cooling the image after the drying step to a temperatureT_(r) of 30° C. or lower in a state where the tension S3 is applied tothe resin base material A.

Examples of the means for cooling the image include cooling means suchas a cooling roll, air blowing means such as a dryer, natural cooling(air cooling), and means combining these.

Examples of the method for cooling the image include a method ofbringing an image-forming surface of the resin base material A and/or animage-non-forming surface thereof into contact with a cooling roll, amethod of applying cold air to an image-forming surface of the resinbase material A, a method of disposing the resin base material A onwhich an image is formed in a space whose temperature is adjusted to thetemperature T_(r) or lower, and a method of combining a plurality ofthese methods.

The temperature T_(r) is preferably in a range of 5° C. to 30° C., morepreferably in a range of 10° C. to 30° C., and still more preferably ina range of 20° C. to 30° C.

The image recording method of the present disclosure may include othersteps as necessary.

Examples of other steps include a step of forming an overcoat layercovering the recorded image and a step of laminating a laminate basematerial on a side of the resin base material A, on which the image hasbeen recorded, where the image is provided.

<One Example of Image Recording Device>

FIG. 2 is a view conceptually illustrating an example of an imagerecording device used for carrying out the image recording method of thepresent disclosure.

As illustrated in FIG. 2, the image recording device according to thepresent example is an example of an image recording device comprising atransport mechanism for transporting the resin base material A accordingto the roll-to-roll method, which is a device that unwinds a resin basematerial A1 having a long film shape, which is wound in a roll shape,using an unwinding device W1, transports the unwound resin base materialA1 in the direction indicated by the block arrow, allows the resin basematerial A1 to pass through an ink applying device IJ1, a drying zoneD1, and a cooling zone C1 in this order, and finally winds the resinbase material using a winding device W2.

Here, the resin base material A1 is an example of the resin basematerial A.

The resin base material A1 is transported in a state where the tensionis applied.

Specifically, the tension S1 is applied to a portion covering from theunwinding device W1 to the front of the drying zone D1, the tension S2is applied to a portion covering from the front of the drying zone D1 tothe front of the cooling zone C1, and the tension S3 is applied to aportion covering from the front of the cooling zone C1 to the windingdevice W2, in the transported resin base material A1.

The tension to be applied to the resin base material A1 may be constantover the entire transport path (that is, the relationship of “tensionS1=tension S2=tension S3” may be established), the variation of thetension S1, the tension S2, and the tension S3 may be reduced to, forexample, 40% or less, or the variation may not be particularlycontrolled.

The image recording device according to the present example may comprisea tension adjusting unit that adjusts the tension S1, the tension S2,and the tension S3.

Examples of the tension adjusting unit include a powder brake providedin the unwinding device W1 and/or the winding device W2, a dancer rollprovided in the middle of a transport path, and a control device (forexample, a tension controller) that controls each tension by adjustingeach condition of the image recording device.

Further, the image recording device according to the present example maycomprise a tension measuring unit (for example, a tension meter) formeasuring the tension S1, the tension S2, and the tension S3.

Since FIG. 2 is a conceptual view, the transport path of the resin basematerial A1 is simplified and shown such that the resin base material A1is transported in one direction, but it goes without saying that thetransport path of the resin base material A1 may meander.

The method of transporting the resin base material A1 can beappropriately selected from various web transport methods of using adrum, a roller, and the like.

The ink applying device IJ1 is disposed on the downstream side of theresin base material A1 in the transport direction (hereinafter, alsosimply referred to as “the downstream side”) with respect to theunwinding device W1 that unwinds the resin base material A1.

In the ink applying device IJ1, the applying step (that is, the applyingstep of applying the ink onto the resin base material A to which thetension S1 is applied, to obtain an image) is performed.

The method of applying the ink is as described in the section of the“applying step”.

A surface treatment unit (not illustrated) that performs a surfacetreatment (preferably, a corona treatment) on the resin base material A1may be provided on the upstream side of the resin base material A1 inthe transport direction with respect to the ink applying device IJ1.

Although not illustrated, the structure of the ink applying device IJ1may be a structure comprising at least one ink jet head.

The ink jet head may be a shuttle head, but a line head in which a largenumber of jetting ports (nozzles) are aligned in the width direction ofthe resin base material A having a long film shape is preferable fromthe viewpoint of speeding up image recording.

From the viewpoint of speeding up of image recording, it is preferablethat the structure of the ink applying device IJ1 is a structurecomprising at least one of a line head for black (K) ink, a line headfor cyan (C) ink, a line head for magenta (M) ink, or a line head foryellow (Y) ink.

As the structure of the ink applying device IJ1, a structure whichcomprises at least two of the above-described four line heads and inwhich two or more of these line heads are aligned in the transportdirection of the resin base material A (the direction indicated by theblock arrow) is more preferable.

The ink applying device IJ1 may further comprise at least one of a linehead for white ink, a line head for orange ink, a line head for greenink, a line head for purple ink, a line head for light cyan ink, or aline head for light magenta ink.

The drying zone D1 is disposed on the downstream side of the inkapplying device IJ1.

In the drying zone D1, the drying step (that is, the drying step ofheating the image to a temperature T_(d) of 50° C. or higher and dryingthe image in a state where a tension S2 of 10 N/m or greater is appliedto the resin base material A) is performed.

The method of drying the image is as described in the section of the“drying step”.

The cooling zone C1 is disposed on the downstream side of the dryingzone D1.

In the cooling zone C1, the cooling step (that is, the cooling step ofcooling the image after the drying step to a temperature T_(r) of 30° C.or lower in a state where the tension S3 is applied to the resin basematerial A) is performed.

The method of cooling the image is as described in the section of the“cooling step”.

In the image recording using the image recording device according to thepresent example, first, the resin base material A1 having a long filmshape which is wound in a roll shape is unwound by the unwinding deviceW1, the unwound resin base material A1 is transported in the directionindicated by the block arrow, an image is formed on the transportedresin base material A1 by performing the above-described applying stepusing the ink applying device IJ1.

Next, the above-described drying step is performed to dry the image inthe drying zone D1, the above-described cooling step is performed tocool the image in the cooling zone C1, and the resin base material A1 onwhich the image is recorded is wound up by the winding device W2.

In the image recording, a decrease in adhesiveness of the image to theresin base material A1 is suppressed by controlling the above-describedσ_(total) to 40 kgf/cm² or less.

EXAMPLES

Hereinafter, examples of the present disclosure will be described below,but the present disclosure is not limited to the following examples.

Hereinafter, “parts” and “%” are on a mass basis unless otherwisespecified.

Further, in the description below, “water” indicates ion exchange waterunless otherwise specified.

[Preparation of Aqueous Dispersion Liquid of Resin X]

As aqueous dispersion liquids of the resin X, an aqueous dispersionliquid of resin particles E1 (specifically, composite particlescontaining a polyester resin and an acrylic resin) as the resin X, anaqueous dispersion liquid of acrylic resin particles AC1 as resin X, andan aqueous dispersion liquid of acrylic resin particles AC2 as resin Xwere respectively prepared.

<Aqueous Dispersion Liquid of Resin Particles E1>

PESRESIN A-615GE (manufactured by Takamatsu Oil & Fat Co., Ltd.) wasprepared as an aqueous dispersion liquid of resin particles E1(specifically, composite particles containing a polyester resin and anacrylic resin).

<Aqueous Dispersion Liquid of Acrylic Resin Particles AC1>

An aqueous dispersion liquid of the acrylic resin particles AC1 wasprepared. Hereinafter, the details will be described.

3.0 g of sodium dodecyl benzene sulfonate (62 mass % aqueous solution,manufactured by Tokyo Chemical Industry Co., Ltd.) and 377 g of waterwere added to a 1000 mL three-neck flask provided with a stirrer and acooling pipe, and the solution was heated to 90° C. in a nitrogenatmosphere. A solution A obtained by adding 9.0 g of a 50 mass % aqueoussolution of sodium 2-acrylamido-2-methylpropane sulfonate (manufacturedby Sigma-Aldrich Co., LLC) to 20 g of water, a solution B obtained bymixing 12.5 g of 2-hydroxyethyl methacrylate (manufactured by FujifilmWako Pure Chemical Corporation), 27.0 g of benzyl acrylate (manufacturedby Tokyo Chemical Industry Co., Ltd.), and 6.0 g of styrene(manufactured by Fujifilm Wako Pure Chemical Corporation), and asolution C obtained by dissolving 6.0 g of sodium persulfate(manufactured by Fujifilm Wako Pure Chemical Corporation) in 40 g ofwater were simultaneously added dropwise to the heated mixed solution inthe three-neck flask for 3 hours. After completion of the dropwiseaddition, the solution was allowed to further react for 3 hours, therebysynthesizing 500 g of an aqueous dispersion liquid of the acrylic resinparticles AC1 (the amount of the solid content of the acrylic resinparticles AC1: 10.1% by mass).

Further, the weight-average molecular weight of the acrylic resin of theacrylic resin particles AC1 was 149000.

<Aqueous Dispersion Liquid of Acrylic Resin Particles AC2>

An aqueous dispersion liquid of the acrylic resin particles AC2 wasprepared. Hereinafter, the details will be described.

3.0 g of sodium dodecyl benzene sulfonate (62 mass % aqueous solution,manufactured by Tokyo Chemical Industry Co., Ltd.) and 376 g of waterwere added to a 1000 mL three-neck flask provided with a stirrer and acooling pipe, and the solution was heated to 90° C. in a nitrogenatmosphere. A solution A obtained by adding 11.0 g of a 50 mass %aqueous solution of sodium 2-acrylamido-2-methylpropane sulfonate(manufactured by Sigma-Aldrich Co., LLC) to 20 g of water, a solution Bobtained by mixing 12.5 g of 2-hydroxyethyl methacrylate (manufacturedby Fujifilm Wako Pure Chemical Corporation), 17.0 g of butylmethacrylate (manufactured by Fujifilm Wako Pure Chemical Corporation),and 15.0 g of styrene (manufactured by Fujifilm Wako Pure ChemicalCorporation), and a solution C obtained by dissolving 6.0 g of sodiumpersulfate (manufactured by Fujifilm Wako Pure Chemical Corporation) in40 g of water were simultaneously added dropwise to the heated mixedsolution in the three-neck flask for 3 hours. After completion of thedropwise addition, the resulting solution was allowed to further reactfor 3 hours, thereby synthesizing 500 g of an aqueous dispersion liquidof the acrylic resin particles AC2 (the amount of the solid content ofthe specific resin 1: 10.1% by mass).

Further, the weight-average molecular weight of the acrylic resin of theacrylic resin particles AC2 was 126000.

<Aqueous Dispersion Liquid of Urethane Resin Particles U1>

SUPERFLEX 620 (manufactured by DKS Co., Ltd.) was prepared as an aqueousdispersion liquid of urethane resin particles U1.

Example 1

<Preparation of Cyan Ink>

A cyan ink with the following composition was prepared.

—Composition of Cyan Ink—

CAB-O-JET450C (manufactured by Cabot Corporation, cyan pigmentdispersion liquid, concentration of pigment: 15% by mass) . . . 2.4% bymass as amount of solid content

1,2-Propanediol (manufactured by Fujifilm Wako Pure ChemicalCorporation) (water-soluble solvent) . . . 20% by mass

OLFINE E1010 (manufactured by Nissin Chemical Co., Ltd.) (surfactant) .. . 1% by mass

Resin particles E1 as resin X . . . 6% by mass as amount of solidcontent of resin particles E1

SNOWTEX (registered trademark) XS (manufactured by Nissan Chemical Co.,Ltd., colloidal silica) . . . 0.06% by mass as amount of solid contentof silica

Water . . . remaining amount set such that total amount of compositionwas 100% by mass

<Preparation of Resin Base Material A>

As the resin base material A, a biaxially stretched polypropylene (OPP)base material “FOR-AQ” (manufactured by Futamura Chemical Co., Ltd.) wasprepared.

“FOR-AQ” is a roll body in which an OPP base material having a thicknessof 25 μm, a width of 580 mm, and a length of 2000 m is wound in a rollshape.

Hereinafter, the OPP base material will be referred to as a “resin basematerial O1”, and the roll body will be referred to as a “roll body 1”.

The distortion rate (a1) of the resin base material O1 was 0.18%.

(Preparation of Image Recording Device)

As the image recording device used for the evaluation, the imagerecording device illustrated in FIG. 2 according to the above-describedexample was prepared.

A tension controller (“LE-40MTA” manufactured by Mitsubishi ElectricCorporation) was incorporated in the image recording device, and thetension S1, the tension S2, and the tension S3 were controlled using thetension controller in image recording described below.

Further, a tension meter (“CJ200” manufactured by Nireco Corporation)that measures the tension S1, the tension S2, and the tension S3 wasincorporated in the image recording device, and the tension S1, thetension S2, and the tension S3 were measured using the tension meter inthe image recording described below.

The ink jet head and the ink jetting conditions for the ink applyingdevice IJ1 were as follows.

Ink jet head: 1200 dpi (dot per inch, 1 inch is 2.54 cm)/20-inch widthpiezo full line head (total number of nozzles: 2048) was used.

Ink droplet amount: set to 2.0 pL

Driving frequency: set to 30 kHz

Warm air drying was used as the drying method in the drying zone D1.

Air cooling was used as the cooling method in the cooling zone C1.

(Image Recording)

The roll body 1 was set in the unwinding device W1 of the imagerecording device.

Next, the resin base material A (OPP base material) was unwound from theroll body 1 by the unwinding device W1, and the unwound resin basematerial A was transported at a transport speed of 635 mm/sec.

Adjustment was made such that a tension of 10 N/m was applied to theresin base material A over the entire transport path of the transportedresin base material A. That is, all the tension S1 applied to a portioncovering from the unwinding device W1 to the front of the drying zoneD1, the tension S2 applied to a portion covering from the front of thedrying zone D1 to the front of the cooling zone C1, and the tension S3applied to a portion covering from the front of the cooling zone C1 tothe winding device W2 were adjusted to 10 N/m.

The above-described cyan ink was applied to the resin base material Aduring transportation in the form of a solid image using the inkapplying device IJ1 according to the ink jet method, thereby obtainingan undried cyan solid image.

Here, the region where the cyan ink was applied was set as a band-shapedregion having a width of 250 mm with a central portion in the widthdirection as a center in a total width of 580 mm of the resin basematerial A1. Here, the mass of the cyan ink to be applied per unit areain the region where the cyan ink was applied was set to 3.5 g/m².

Next, the solid image in the resin base material A transported from theink applying device IJ1 was heated under a condition that the reachedtemperature (temperature T_(d)) was set to 60° C. and the drying time(that is, the time from the start of heating to the start of cooling)was set to 8 seconds in the drying zone D1 and dried.

Next, the solid image (that is, the solid image after being dried) inthe resin base material A transported from the drying zone D1 was cooledto 25° C. (temperature T_(r)).

The solid image was cooled, and the resin base material A (that is, theimage recorded material in which the solid image was recorded on theresin base material A) was wound by the winding device W2.

Hereinafter, the wound image recorded material will be referred to as a“roll body 2”.

The roll body 2 was allowed to stand at 25° C. for 1 hour.

As described above, a cyan solid image was recorded on the entireband-shaped region having a width of 250 mm on the resin base materialA.

The thickness of the cyan solid image was 1.85 μm.

The thickness of the cyan solid image was measured by observing a crosssection of the cyan solid image with a scanning electron microscope(SEM) at a magnification of 10000 times.

<Measurement of E(T_(d))>

E(T_(d)) was measured by the above-described method using the aqueousdispersion liquid of the resin X.

The results are listed in Table 1.

<Measurement of ε(T_(d))>

E(T_(d)) was measured by the above-described method using the resin basematerial A.

The results are listed in Table 1.

<Calculation of σ_(dry)>

σ_(dry) was calculated by Equation (2) based on E(T_(d)) and ε(T_(d)).

The results are listed in Table 1.

<Measurement of E(T), α_(r)(T), and α_(s)(T)>

E(T), α_(r)(T), and α_(s)(T) were measured for each temperature Tobtained by dividing a range of the temperature Tr or higher and thetemperature T_(d) or lower at intervals of 0.1° C. using the aqueousdispersion liquid of the resin X and the resin base material A accordingto the above-described methods.

The notation of the result is not provided.

<Calculation of σ_(cool)>

“E(T)(α_(r)(T)−α_(s)(T))” at each temperature T was acquired based onthe results of E(T), α_(r)(T), and α_(s)(T) at each temperature T.

σ_(cool) was acquired by Equation (3) based on the obtained result of“E(T)(α_(r)(T)−α_(s)(T))”.

Specifically, a graph showing the relationship between the temperature Tand “E(T)(α_(r)(T)−α_(s)(T))” was prepared, an area enclosed by thecurve of the obtained graph, the straight line showing the temperatureT_(r), the straight line showing the temperature T_(d), and the straightline in which “E(T)(α_(r)(T)−α_(s)(T))” was 0 was acquired, and obtainedarea was set to σ_(cool).

The results are listed in Table 1.

The graph in Example 1 is shown in FIG. 1.

<Calculation of σ_(total)>

σ_(total) was calculated by Equation (1) based on the results of σ_(dry)and σ_(cool).

The results are listed in Table 1.

<Evaluation of Adhesiveness of Image>

Next, the adhesiveness of the image was evaluated by unwinding the imagerecorded material from the roll body 2 that had been allowed to stand at25° C. for 1 hour, attaching a piece of tape of Cellotape (registeredtrademark, No. 405, manufactured by Nichiban Co., Ltd., width of 12 mm,hereinafter, also simply referred to as “tape”) onto the cyan solidimage on the unwound image recorded material, and peeling the piece oftape off from the cyan solid image.

Specifically, the tape was attached and peeled off according to thefollowing method.

The tape was taken out at a constant speed and cut to have a length of75 mm, thereby obtaining a piece of tape.

The obtained piece of tape was superimposed on the cyan solid image, anda region at the central portion of the piece of tape with a width of 12mm and a length of 25 mm was attached onto the image using a finger andrubbed firmly with a fingertip.

The end of the piece of tape was grabbed in 5 minutes after attachmentof the piece of tape and peeled at an angle as close to 60° as possiblein 0.5 seconds to 1.0 seconds.

The presence or absence of adhesive matter on the piece of peeled tapeand the presence or absence of peeling of the cyan solid image on theresin base material A were visually observed, and the adhesiveness ofthe image was evaluated based on the following evaluation standards.

The results are listed in Table 1.

—Evaluation Standards for Adhesiveness of Image—

5: Adhesive matter was not found on the piece of tape, and peeling ofthe image on the resin base material A was not found.

4: A small amount of colored adhesive matter was found on the piece oftape, but peeling of the image on the resin base material A was notfound.

3: A small amount of colored adhesive matter was found on the piece oftape, and slight peeling of the image on the resin base material A wasfound, but it was in a practically acceptable range.

2: Colored adhesive matter was found on the piece of tape, peeling ofthe image on the resin base material A was found, and it was out of apractically acceptable range.

1: Colored adhesive matter was found on the piece of tape, most of theimage on the resin base material A was peeled off, and the resin basematerial A was visually recognized.

Examples 2 to 8 and Comparative Examples 1 to 3

The same operation as in Example 1 was performed except that thecombinations of the kind of the resin base material A, the kind of theresin X, the tension S1, the tension S2, the tension S3, the temperatureT_(d), and the temperature T_(r) were changed as listed in Table 1.

The results are listed in Table 1.

A resin base material N1 as the resin base material A is asimultaneously biaxially stretched nylon base material “EMBLEM(registered trademark) ON-15” (manufactured by Unitika Ltd., a roll bodyin which a nylon base material having a thickness of 15 μm, a width of580 mm, and a length of 2000 m is wound in a roll shape). The distortionrate (a1) of the resin base material N1 was −0.26%.

A resin base material HDPE as the resin base material A is a monoaxiallystretched high-density polyethylene base material “PE3K-BT”(manufactured by Futamura Chemical Co., Ltd., a roll body in which abase material having a thickness of 23 μm, a width of 580 mm, and alength of 2000 m is wound in a roll shape). The distortion rate (a1) ofthe resin base material HDPE was 0.23%.

TABLE 1 Applying Resin base material A step Drying step Cooling stepDistortion Resin X S1 S2 T_(d) S3 T_(r) Type rate (%) in ink (N/m) (N/m)(° C.) (N/m) (° C.) Example 1 O1 0.18 E1 10 10 60 10 25 Example 2 O10.18 AC1 10 10 60 10 25 Example 3 O1 0.18 AC2 10 10 60 10 25 Example 4O1 0.18 AC1 30 30 60 30 25 Comparative O1 0.18 E1 10 10 70 10 25 Example1 Comparative O1 0.18 E1 10 10 80 10 25 Example 2 Comparative N1 −0.26E1 10 10 60 10 25 Example 3 Example 5 N1 −0.26 AC1 10 10 60 10 25Example 6 N1 −0.26 AC2 10 10 60 10 25 Example 7 N1 −0.26 E1 30 30 60 3025 Example 8 N1 −0.26 AC1 30 30 60 30 25 Example 9 HDPE 0.23 E1 10 10 6010 25 Example 10 HDPE 0.23 AC1 10 10 60 10 25 Example 11 HDPE 0.23 AC210 10 60 10 25 Example 12 HDPE 0.23 AC1 10 10 80 10 25 Example 13 HDPE0.23 AC1 30 30 60 30 25 Example 14 O1 0.18 U1 10 10 60 10 25 Example 15N1 −0.26 AC1 10 10 50 10 25 Comparative N1 −0.26 AC2 10 10 50 10 25Example 4 E(T_(d)) σ_(dry) σ_(cool) σ_(total) (kgf/cm²) ε(T_(d))(kgf/cm²) (kgf/cm²) (kgf/cm²) Adhesiveness Example 1 7100 5.0 × 10⁻⁵0.36 −27 27 4 Example 2 20 5.0 × 10⁻⁵ 0.0010 0.10 0 4 Example 3 8200 5.0× 10⁻⁵ 0.41 −14 14 4 Example 4 20 1.8 × 10⁻³ 0.036 −0.10 0 4 Comparative3700 −1.3 × 10⁻³  −4.8 −38 43 1 Example 1 Comparative 2500 −3.8 × 10⁻³ −9.5 −44 54 1 Example 2 Comparative 7100 −5.3 × 10⁻³  −38 −15 53 1Example 3 Example 5 20 −5.3 × 10⁻³  −0.11 2.1 2 5 Example 6 8200 −5.3 ×10⁻³  −43 7.9 35 3 Example 7 7100 −2.6 × 10⁻³  −19 −12 31 3 Example 8 20−2.6 × 10⁻³  −0.052 2.1 2 5 Example 9 7100 1.0 × 10⁻³ 7.1 −42 35 3Example 10 20 1.0 × 10⁻³ 0.020 −2.3 2 5 Example 11 8200 1.0 × 10⁻³ 8.2−30 22 4 Example 12 5.1 2.2 × 10⁻³ 0.011 −2.9 3 5 Example 13 20 2.3 ×10⁻³ 0.046 −2.2 2 5 Example 14 5700 5.0 × 10⁻⁵ 0.29 −12 11 4 Example 1550 −4.5 × 10⁻³  −0.23 1.7 2 5 Comparative 13000 −4.5 × 10⁻³  −59 5.5 531 Example 4

As listed in Table 1, in Examples 1 to 15 in which csioiai was 40kgf/cm² or less, the adhesiveness of the image to the resin basematerial A was excellent as compared with Comparative Examples 1 to 4 inwhich σ_(total) was greater than 40 kgf/cm².

It was confirmed that in a case where σ_(total) was 30 kgf/cm² or less,the adhesiveness of the image to the resin base material A was furtherimproved.

As described above, the example group using the cyan ink as the ink hasbeen described. However, it goes without saying that the same effects asthose of the above-described example group can be obtained even in acase where the cyan ink was changed to an ink other than the cyan ink(for example, magenta ink, yellow ink, or black ink) in the examplegroup or in a case where a polychromic image was recorded using the cyanink and at least one ink other than the cyan ink.

The disclosure of JP2019-137001 filed on Jul. 25, 2019 is incorporatedherein by reference in its entirety.

In a case where all documents, patent applications, and technicalstandards described in the present specification are specified to beincorporated specifically and individually as cited documents, thedocuments, patent applications, and technical standards are incorporatedherein in the same limited scope as the cited documents.

What is claimed is:
 1. An image recording method comprising: preparing aresin base material A in which an absolute value of a distortion raterepresented by Equation (a1) in a case where the base material is heatedfrom 25° C. to 60° C. at a temperature increasing rate of 5° C./min andmaintained at 60° C. for 2 minutes in a state where a tension of 30 N/mis applied thereto, and the base material is cooled to 25° C. at atemperature decreasing rate of 5° C./min in a state where a tension of30 N/m is applied thereto is 0.05% or greater; preparing an inkcontaining water, a resin X, and a colorant; applying the ink onto theresin base material A to which a tension S1 of 10 N/m or greater isapplied, to obtain an image; heating and drying the image to atemperature T_(d) of 50° C. or higher in a state where a tension S2 of10 N/m or greater is applied to the resin base material A; and coolingthe image after the drying to a temperature T_(r) of 30° C. or lower ina state where a tension S3 of 10 N/m or greater is applied to the resinbase material A, wherein σ_(total) to be calculated by Equation (1) is40 kgf/cm² or less,distortion rate (%)=((length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating)×100  Equation (a1)σ_(total)=|σ_(dry)+σ_(cool)|  Equation (1)σ_(dry) =E(T _(d))ε(T _(d))  Equation (2)σ_(cool) =∫E _(T) _(r) ^(T) ^(d) (T)(α_(r)(T)−α_(s)(T))dT  Equation (3)in Equation (1), σ_(dry) is calculated by Equation (2), and σ_(cool) iscalculated by Equation (3), in Equation (2), E(T_(d)) represents anelastic modulus of the resin X at the temperature T_(d) which isexpressed in a unit of kgf/cm², ε(T_(d)) represents an expansioncoefficient of the length of the resin base material A represented byEquation (a2) in the tension application direction in a case where thebase material is heated from 25° C. to the temperature T_(d) andmaintained at the temperature T_(d) in a state where the tension S2 isapplied thereto, and the base material is cooled to 25° C. in a statewhere the tension S2 is applied thereto,expansion coefficient of length of resin base material A in tensionapplication direction=(length of resin base material in tensionapplication direction at end of cooling−length thereof in tensionapplication direction at start of heating)/length thereof in tensionapplication direction at start of heating  Equation (a2) in Equation(3), E(T) represents an elastic modulus of the resin X at a temperatureT of the image in the cooling which is expressed in the unit of kgf/cm²,α_(r)(T) represents a linear expansion coefficient of the resin X at thetemperature T, α_(s)(T) represents a linear expansion coefficient of theresin base material A in the tension application direction in a statewhere the tension S3 is applied thereto at the temperature T, T_(d)represents the temperature T_(d), and T_(r) represents the temperatureT_(r).
 2. The image recording method according to claim 1, whereinσ_(total) is 30 kgf/cm² or less.
 3. The image recording method accordingto claim 1, wherein the tension S1, the tension S2, and the tension S3are each independently in a range of 10 N/m to 60 N/m.
 4. The imagerecording method according to claim 1, wherein the resin base material Ahas a thickness of 12 nm to 60 nm.
 5. The image recording methodaccording to claim 1, wherein the resin base material A is apolypropylene base material or a nylon base material.
 6. The imagerecording method according to claim 1, wherein the resin X is at leastone of an acrylic resin or a polyester resin.
 7. The image recordingmethod according to claim 1, wherein the resin base material A has along film shape, and the application of the ink in the applying, thedrying of the image in the drying, and the cooling of the image in thecooling are performed while the resin base material A is transported ina longitudinal direction of the resin base material A using aroll-to-roll method.